Split sleeves for rolling cutters

ABSTRACT

A cutter assembly may include a multi-piece split sleeve, an inner cutting element having a groove or protrusion formed in a side surface thereof and disposed in the multi-piece split sleeve, and at least one component interfacing at least a portion of the groove or the protrusion to limit axial movement of the inner cutting element with respect to the multi-piece split sleeve, in which the multiple pieces of the split sleeve are joined together at an overlapping joint.

BACKGROUND

1. Technical Field

Embodiments disclosed herein relate generally to polycrystalline diamond compact cutters and bits or other cutting tools incorporating the same. More particularly, embodiments disclosed herein relate to cutters retained within a sleeve and/or rolling cutters having curved transitions and bits or other cutting tools incorporating the same.

2. Background Art

Various types and shapes of earth boring bits are used in various applications in the earth drilling industry. Earth boring bits have bit bodies which include various features such as a core, blades, and cutter pockets that extend into the bit body or roller cones mounted on a bit body, for example. Depending on the application/formation to be drilled, the appropriate type of drill bit may be selected based on the cutting action type for the bit and its appropriateness for use in the particular formation.

Drag bits, often referred to as “fixed cutter drill bits,” include bits that have cutting elements attached to the bit body, which may be a steel bit body or a matrix bit body formed from a matrix material such as tungsten carbide surrounded by a binder material. Drag bits may generally be defined as bits that have no moving parts. However, there are different types and methods of forming drag bits that are known in the art. For example, drag bits having abrasive material, such as diamond, impregnated into the surface of the material which forms the bit body are commonly referred to as “impreg” bits. Drag bits having cutting elements made of an ultra hard cutting surface layer or “table” (typically made of polycrystalline diamond material or polycrystalline boron nitride material) deposited onto or otherwise bonded to a substrate are known in the art as polycrystalline diamond compact (“PDC”) bits.

PDC bits drill soft formations easily, but they are frequently used to drill moderately hard or abrasive formations. They cut rock formations with a shearing action using small cutters that do not penetrate deeply into the formation. Because the penetration depth is shallow, high rates of penetration are achieved through relatively high bit rotational velocities.

PDC cutters have been used in industrial applications including rock drilling and metal machining for many years. In PDC bits, PDC cutters are received within cutter pockets, which are formed within blades extending from a bit body, and are typically bonded to the blades by brazing to the inner surfaces of the cutter pockets. The PDC cutters are positioned along the leading edges of the bit body blades so that as the bit body is rotated, the PDC cutters engage and drill the earth formation. In use, high forces may be exerted on the PDC cutters, particularly in the forward-to-rear direction. Additionally, the bit and the PDC cutters may be subjected to substantial abrasive forces. In some instances, impact, vibration, and erosive forces have caused drill bit failure due to loss of one or more cutters, or due to breakage of the blades.

In a typical application, a compact of polycrystalline diamond (PCD) for other ultrahard material) is bonded to a substrate material, which is typically a sintered metal carbide to form a cutting structure. PCD comprises a polycrystalline mass of diamonds (typically synthetic) that are bonded together to form an integral, tough, high-strength mass or lattice. The resulting PCD structure produces enhanced properties of wear resistance and hardness, making PCD materials extremely useful in aggressive wear and cutting applications where high levels of wear resistance and hardness are desired.

A PDC cutter is conventionally formed by placing a sintered carbide substrate into the container of a press. A mixture of diamond grains or diamond grains and catalyst binder is placed atop the substrate and treated under high pressure, high temperature conditions. In doing so, metal binder (often cobalt) migrates from the substrate and passes through the diamond grains to promote intergrowth between the diamond grains. As a result, the diamond grains become bonded to each other to form the diamond layer, and the diamond layer is in turn integrally bonded to the substrate. The substrate often comprises a metal-carbide composite material, such as tungsten carbide-cobalt. The deposited diamond layer is often referred to as the “diamond table” or “abrasive layer.”

An example of a prior art PDC bit having a plurality of cutters with ultra hard working surfaces is shown in FIGS. 1A and 1B. The drill bit 100 includes a bit body 110 having a threaded upper pin end 111 and a cutting end 115. The cutting end 114 typically includes a plurality of ribs or blades 120 arranged about the rotational axis L (also referred to as the longitudinal or central axis) of the drill bit and extending radially outward from the bit body 210. Cutting elements, or cutters, 150 are embedded in the blades 120 at predetermined angular orientations and radial locations relative to a working surface and with a desired back rake angle and side rake angle against a formation to be drilled.

A plurality of orifices 116 are positioned on the bit body 110 in the areas between the blades 120, which may be referred to as “gaps” or “fluid courses,” The orifices 116 are commonly adapted to accept nozzles. The orifices 116 allow drilling fluid to be discharged through the bit in selected directions and at selected rates of flow between the blades 120 for lubricating and cooling the drill bit 100, the blades 120 and the cutters 150. The drilling fluid also cleans and removes the cuttings as the drill bit 100 rotates and penetrates the geological formation. Without proper flow characteristics, insufficient cooling of the cutters 150 may result in cutter failure during drilling operations. The fluid courses are positioned to provide additional flow channels for drilling fluid and to provide a passage for formation cuttings to travel past the drill bit 100 toward the surface of a wellbore (not shown).

Referring to FIG. 1B, a top view of a prior art PDC bit is shown. The cutting face 118 of the bit shown includes six blades 120. Each blade includes a plurality of cutting elements or cutters generally disposed radially from the center of cutting face 118 to generally form rows. Certain cutters, although at differing axial positions, may occupy radial positions that are in similar radial position to other cutters on other blades.

Cutters are conventionally attached to a drill bit or other downhole tool by a brazing process. In the brazing process, a braze material is positioned between the cutter and the cutter pocket. The material is melted and, upon subsequent solidification, bonds (attaches) the cutter in the cutter pocket. Selection of braze materials depends on their respective melting temperatures, to avoid excessive thermal exposure (and thermal damage) to the diamond layer prior to the bit (and cutter) even being used in a drilling operation. Specifically, alloys suitable for brazing cutting elements with diamond layers thereon have been limited to only a couple of alloys which offer low enough brazing temperatures to avoid damage to the diamond layer and high enough braze strength to retain cutting elements on drill bits.

A significant factor in determining the longevity of PDC cutters is the exposure of the cutter to heat. Conventional polycrystalline diamond is stable at temperatures of up to 700-750° C. in air, above which observed increases in temperature may result in permanent damage to and structural failure of polycrystalline diamond. This deterioration in polycrystalline diamond is due to the significant difference in the coefficient of thermal expansion of the binder material, cobalt, as compared to diamond. Upon heating of polycrystalline diamond, the cobalt and the diamond lattice will expand at different rates, which may cause cracks to form in the diamond lattice structure and result in deterioration of the polycrystalline diamond. Damage may also be due to graphite formation at diamond-diamond necks leading to loss of microstructural integrity and strength loss, at extremely high temperatures.

Exposure to heat (through brazing or through frictional heat generated from the contact of the cutter with the formation) can cause thermal damage to the diamond table and eventually result in the formation of cracks (due to differences in thermal expansion coefficients) which can lead to spalling of the polycrystalline diamond layer, delamination between the polycrystalline diamond and substrate, and conversion of the diamond back into graphite causing rapid abrasive wear. As a cutting element contacts the formation, a wear flat develops and frictional heat is induced. As the cutting element is continued to be used, the wear flat will increase in size and further induce frictional heat. The heat may build-up that may cause failure of the cutting element due to thermal mis-match between diamond and catalyst discussed above. This is particularly true for cutters that are immovably attached to the drill bit, as conventional in the art.

Accordingly, there exists a continuing need to develop ways to extend the life of a cutting element.

SUMMARY OF INVENTION

This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

According to one aspect, embodiments disclosed herein relate to a cutter assembly that includes a multi-piece split sleeve, an inner cutting element having a groove or protrusion formed in a side surface thereof and disposed in the multi-piece split sleeve, and at least one component interfacing at least a portion of the groove or the protrusion to limit axial movement of the inner cutting element with respect to the multi-piece split sleeve, in which the multiple pieces of the split sleeve are joined together at an overlapping joint.

According to another aspect, embodiments disclosed herein relate to a cutting tool that includes a tool body, a plurality of blades extending from the tool body, at least one cutter pocket formed in the plurality of blades, at least one cutter assembly disposed in the at least one cutter pocket, the at least one cutter assembly including a multi-piece split sleeve, an inner cutting element having a groove or protrusion formed in a side surface thereof and disposed in the multi-piece split sleeve, and at least one component interfacing at least a portion of the groove or the protrusion to limit axial movement of the inner cutting element with respect to the multi-piece split sleeve, in which the multiple pieces of the split sleeve are jointed together at an overlapping joint, in which the multi-piece sleeve is brazed into the at least one cutter pocket.

According to another aspect, embodiments disclosed herein relate to a cutting tool that includes a tool body, a plurality of blades extending from the tool body, at least one rotatable cutting element disposed on at least one blade, in which the rotatable cutting element has a groove formed in a side surface thereof, and at least one retention element interfacing the rotatable cutting element at the groove and limiting axial movement of the rotatable cutting element, in which the rotatable cutting element includes a smooth and curved transition between the groove and the neighboring side surface.

Other aspects and advantages of the claimed subject matter will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B show a side and top view of a conventional drag bit.

FIGS. 2A and 2B show a side and top cross-sectional view of an inner cutting element disposed within a multi-piece split sleeve, in which the sleeve extends around only a portion of the circumference of the inner cutting element, according to embodiments disclosed herein.

FIGS. 3A and 3B show a side and top cross-sectional view of an inner cutting element disposed within a multi-piece split sleeve, in which the sleeve extends around the entire circumference of the inner cutting element, according to embodiments disclosed herein.

FIG. 4 shows a cross-sectional view of an inner cutting element disposed within a sleeve, in which the inner cutting element includes a smooth and curved transition between the groove and the neighboring side surface, according to embodiments disclosed herein.

FIG. 5 shows a cross-sectional view of an inner cutting element disposed within a sleeve, in which a bottom surface of the inner cutting element has curvature, according to embodiments disclosed herein.

FIGS. 6A and 6B show a side and top view of an inner cutting element having a groove formed in a side surface thereof, in which the protrusion extends around only a portion of the inner cutting element, according to embodiments disclosed herein.

FIG. 7 shows a cross-sectional view of an inner cutting element disposed within a sleeve, in which an outer diameter of the sleeve is equal to an outer diameter of the inner cutting element, according to embodiments disclosed herein.

FIG. 8 shows a cross-sectional view of an inner cutting element disposed within a sleeve, in which the inner cutting element includes a smooth and curved transition between the groove and the neighboring side surface, and in which an outer diameter of the sleeve is equal to an outer diameter of the inner cutting element, according to embodiments disclosed herein.

FIG. 9 shows a perspective view of a cutter assembly disposed in a cutter pocket, according to embodiments of the present disclosure.

FIG. 10 shows an exploded view of a cutter assembly and a cutter pocket, according to embodiments of the present disclosure.

FIG. 11 shows a cross-sectional view of a cutter assembly disposed in a cutter pocket, according to embodiments of the present disclosure.

FIG. 12 shows a perspective view of a partial sleeve according to embodiments of the present disclosure.

FIG. 13 shows a perspective view of a partial sleeve according to embodiments of the present disclosure.

DETAILED DESCRIPTION

In one aspect, embodiments disclosed herein relate to polycrystalline diamond compact cutters being retained on a drill bit or other cutting tool by a mechanism that interfaces the cutter along a side surface thereof such that the cutter is free to rotate about its longitudinal axis or is mechanically retained therein. Embodiments of the present disclosure also relate to a cutting element having curved transitional surfaces that is retained within a sleeve structure or directly within a cutter pocket. Illustrations of each of these embodiments are shown.

Certain terms are used throughout the following description and claims refer to particular features or components. As those having ordinary skill in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . . ” Further, the terms “axial” and “axially” generally mean along or substantially parallel to a central or longitudinal axis, while the terms “radial” and “radially” generally mean perpendicular to a central, longitudinal axis.

Referring to FIGS. 2A and 2B, an inner cutting element 200 disposed within a multi-piece split sleeve 210, in which the sleeve 210 extends around only a portion of the circumference of the inner cutting element 200, in accordance with embodiments disclosed herein, is shown.

In one or more embodiments, the inner cutting element 200 may be a rotatable cutting element that may be rotatable (about its axis L) within the sleeve 210. Further, in one or more embodiments, the inner cutting element 200 may include an ultrahard layer 202 that forms a cutting face and edge and a substrate 204. In one or more embodiments, the inner cutting element 200 may have a groove 206 formed in a side surface thereof. As shown in FIG. 2A, the inner cutting element 200 has the groove 206 formed in the substrate 204.

In one or more embodiments, at least one component may interface at least a portion of the groove 206 to limit axial movement of the inner cutting element 200 with respect to the sleeve 210. As shown, the sleeve 210 includes a protrusion 208 that is configured to engage or interface with the groove 206 of the inner cutting element 200. In one or more embodiments, the axial movement or displacement of the inner cutting element 200 may be limited by this engagement between the at least one component (e.g., the protrusion 208 of the sleeve 210) and the groove 206 of the inner cutting element 200.

Alternatively, in one or more embodiments, the inner cutting element 200 may include a protrusion (not shown) formed on a side surface thereof instead of the groove 206. Further, in one or more embodiments, the sleeve 210 may include a corresponding groove (not shown) configured to engage or interface with the protrusion of the inner cutting element 200 instead of the protrusion 208. As such, in one or more embodiments, axial movement or displacement of the inner cutting element 200 with respect to the sleeve 210 may be limited by an engagement between the protrusion of the inner cutting element 200 and the groove of the sleeve 210.

In one or more embodiments, the groove 206 of the inner cutting element 200 may extend circumferentially around the entire inner cutting element 200, and the corresponding protrusion 208 of the sleeve 210 may also extend circumferentially around the entire extent of the sleeve 210. Alternatively, in one or more embodiments, the groove 206 of the inner cutting element 200 may extend around only a portion of the inner cutting element 200. In other words, in one or more embodiments, the groove 206 of the inner cutting element 200 may not extend around the entire circumference of the inner cutting element 200.

As discussed above, one or more embodiments may include a protrusion (not shown) formed on the inner cutting element 200 instead of the groove 206, and the sleeve 210 may include a corresponding groove (not shown) configured to engage with the protrusion of the inner cutting element 200 instead of the protrusion 208. As such, in one or more embodiments, the protrusion formed on the inner cutting element 200 may extend circumferentially around the entire cutting element 200, and the corresponding groove of the sleeve 210 may also extend circumferentially around the entire extent of the sleeve 210. Alternatively, in one or more embodiments, the protrusion formed on the inner cutting element 200 may extend around only a portion of the inner cutting element 200. In other words, in one or more embodiments, the protrusion of the inner cutting element 200 may not extend around the entire circumference of the inner cutting element 200.

In one or more embodiments, although the groove 206 (or protrusion) of the inner cutting element 200 may extend around only a portion of the inner cutting element 200 and may not extend around the entire circumference of the inner cutting element 200, the corresponding protrusion 208 (or groove) of the sleeve 210 may extend around the entire circumference of the inner cutting element 200. This may allow the inner cutting element 200 to be rotatable within the sleeve 210 while still restricting axial movement or displacement of the inner cutting element 200 with respect to the sleeve 210.

Alternatively, as will be discussed below, in one or more embodiments, the corresponding protrusion 208 (or groove) of the sleeve 210 may also only extend around a portion of sleeve 210 and may be formed to engage with the groove 206 (or protrusion) of the inner cutting element 200. This may restrict both rotation of the inner cutting element 200 within the sleeve 210 and axial movement or displacement of the inner cutting element 200 with respect to the sleeve 210.

Furthermore, as shown in FIG. 2A, the sleeve split of the split sleeve 210 may include at least two inner surface radii: a first sleeve radius RS1 being smaller than a second sleeve radius RS2. In one or more embodiments, the inner cutting element 200 may include a side surface having at least two radii: a first cutting element radius RC1 being smaller than a second cutting element radius RC2 and axially positioned between a cutting face the ultrahard layer 202 of the inner cutting element 200) and the second cutting element radius RC2. In one or more embodiments, the sleeve 210 is adjacent to at least a portion of the inner cutting element 200 side surface (e.g., a surface of the substrate 204), such that the first sleeve radius RS1 mates or engages with the first cutting element at radius RC1) such that first sleeve radius RS1 mates or engages with first cutting element radius RC1 and the second sleeve radius RS2 mates or engages with the second cutting element radius RC2.

Thus, in one or more embodiments, the interfacing component interfacing at least a portion of the groove or the protrusion of an inner cutting element to limit axial movement of the inner cutting element may be the sleeve 210. For example, as shown in FIG. 2A, the interfacing component to limit axial movement of the inner cutting element 200 with respect to the sleeve 210 is the protrusion 208 of the sleeve 210. Alternatively, in one or more embodiments, the interfacing component may be a separate component from the sleeve. For example, an alternate interfacing component (not shown), such as retention balls or a pin, may be disposed between the sleeve 210 and the inner cutting element 200 that may limit axial movement or displacement of the inner cutting element 200 relative to the sleeve 210.

As shown in FIG. 2B, the multi-piece split sleeve 210 is a two-piece split sleeve. Those having ordinary skill in the art will appreciate that the multi-piece split sleeve may be formed from more than two pieces. For example, in one or more embodiments, the multi-piece split sleeve may be a three-piece, four-piece, five-piece, or more, split sleeve.

Further, as shown in FIG. 2B, the two pieces of the split sleeve 210 are joined together at an overlapping joint 212. As discussed above, in one or more embodiments, the multi-piece split sleeve may be formed from two or more pieces. As such, in one or more embodiments, an overlapping joint (e.g., the overlapping joint 212) may be formed where any pieces of the split sleeve 210 are joined together or engaged at multiple sets of interfacing surfaces (each set of interfacing surfaces angled with respect to one another) instead a single set of mating parallel surfaces. Generally, mating, parallel surfaces may assist in capillary flow of a braze material into a gap between the surface that may be formed when the parallel surfaces are close enough to assist capillary attraction because an adhesive force between a solid and a liquid being greater than cohesive forces within the liquid. As such, an overlapping joint (e.g., the overlapping joint 212) may be sufficient to resist capillary flow of braze material between the pieces of the split sleeve 210 when the sleeve is brazed in a cutter pocket in a bit or other downhole cutting tool. As shown in FIG. 2B, the overlapping joint 212 has three sets of mating surfaces, with each set being substantially perpendicular to the adjacent set(s). However, more or less sets of mating surfaces and other angles may be used to create an overlapping joint.

In one or more embodiments, the overlapping joint 212 may run substantially parallel to a line (not shown) that is tangent to the circumference inner cutting element 200. In one or more embodiments, the overlapping joint 212 may be substantially parallel to a line (not shown) that is tangent to the circumference of the split sleeve 210. Alternatively, in one or more embodiments, the overlapping joint 212 may not necessarily be parallel to a line that is tangent to the circumference of the inner cutting element 200 or tangent to the circumference of the split sleeve 210. For example, in one or more embodiments, the overlapping joint 212 may be angled or slanted and may not be parallel to a line that is tangent to the circumference of the inner cutting element 200 or tangent to the circumference of the split sleeve 210.

Furthermore, as shown in FIG. 2B, the multi-piece split sleeve 210 may extend around only a portion of the circumference of the inner cutting element 200. In one or more embodiments, the sleeve 210 may extend around greater than 180 degrees of the inner cutting element. In other words, in one or more embodiments, the sleeve 210 may extend at least 180 degrees around the circumference of the inner cutting element 200. This may allow the inner cutting element that is disposed within the sleeve 210 to be secured within the sleeve 210 without the sleeve 210 extending around the entire circumference of the inner cutting element 200. In a particular embodiment, the sleeve 210 may extend anywhere from greater than 180 degrees up to 360 degrees around the inner cutting element. Other embodiments, circumferential extent of the sleeve may be from any of a lower limit of 180, 190, 225, 270, or 315 degrees to any of an upper limit of 225, 270, 315, or 360 degrees, with any lower limit being use with any upper limit.

Referring to FIGS. 3A and 3B, an inner cutting element 300 disposed within a multi-piece split sleeve 310, in which the sleeve 310 extends around the entire circumference of the inner cutting element 300, in accordance with embodiments disclosed herein, is shown.

In one or more embodiments, the inner cutting element 300 may be a rotatable cutting element that may be rotatable about its axis L within the sleeve 310. Further, in one or more embodiments, the inner cutting element 300 may include an ultrahard layer 302 and a substrate 304. In one or more embodiments, the inner cutting element 300 may have a groove 306 formed in a side surface thereof. As shown, the inner cutting element 300 has the groove 306 formed in the substrate 304.

In one or more embodiments, at least one component may interface at least a portion of the groove 306 to limit axial movement of the inner cutting element 300 with respect to the sleeve 310. As shown, the sleeve 310 includes a protrusion 308 that is configured to engage or interface with the groove 306 of the inner cutting element 300. However, as discussed above, other interfacing components may be used as well. In one or more embodiments, the axial movement or displacement of the inner cutting element 300 may be limited by this engagement between the at least one component (e.g., the protrusion 308 of the sleeve 310) and the groove 306 of the inner cutting element 300. As discussed above with respect to FIGS. 2A-B, mating groove 306 and/or protrusion 308 may around the entire circumference of inner cutting element 300 or some lesser portion.

As shown, the sleeve 310 extends around the entire circumference of the inner cutting element 300. Further, as shown, the sleeve 310 is a two-piece split sleeve with two overlapping joints 312. As discussed above, an overlapping joint (e.g., the overlapping joints 312) may be formed where any pieces of the split sleeve 310 are joined together or engaged. Further, as discussed above, those having ordinary skill in the art will appreciate that the multi-piece split sleeve may be formed from more than two pieces. For example, in one or more embodiments, the multi-piece split sleeve may be a three-piece, four-piece, five-piece, or more, split sleeve. Furthermore, as discussed above, an overlapping joint (e.g., the overlapping joint 312), similar to the one described with respect to FIGS. 2A-B may be provided at joining of the multiple pieces of sleeve that is overlapping in an amount sufficient to resist capillary flow of braze material between the pieces of the split sleeve 310. Further, while the embodiment illustrated in FIG. 2B only possesses a single overlapping joint 212, the embodiment illustrated in FIG. 3B includes two overlapping joints 312, one at each point at which the multiple sleeve pieces are joined together.

Referring to FIG. 4, an inner cutting element 400 disposed within a sleeve 410 (optionally a multi-piece sleeve, as described above), in which the inner cutting element 400 includes a smooth and curved transition 407 between a groove 406 and a neighboring side surface, in accordance with embodiments disclosed herein, is shown.

In one or more embodiments, the inner cutting element 400 may be a rotatable cutting element that may be rotatable within the sleeve 410. Further, in one or more embodiments, the inner cutting element 400 may include an ultrahard layer 402 and a substrate 404. In one or more embodiments, the inner cutting element 400 may have a groove 406 formed in a side surface thereof. As shown, the inner cutting element 400 has the groove 406 formed in the substrate 404.

In one or more embodiments, at least one component may interface at least a portion of the groove 406 to limit axial movement of the inner cutting element 400 with respect to the sleeve 410. As shown, the sleeve 410 includes a protrusion 408 that is configured to engage or interface with the groove 406 of the inner cutting element 400. In one or more embodiments, the axial movement or displacement of the inner cutting element 400 may be limited by this engagement between the at least one interfacing component (e.g., the protrusion 408 of the sleeve 410) and the groove 406 of the inner cutting element 400.

As shown, the inner cutting element 400 includes smooth and curved transitions 407 between the groove 406 and the neighboring side surface, e.g., an outer surface of the substrate 404. Accordingly, in one or more embodiments, the sleeve 410 includes corresponding smooth and curved transitions between the protrusion 408 and the neighboring side surfaces, e.g., an inner surface of the sleeve 410, to engage or interface with the inner cutting element 400.

As discussed above, in one or more embodiments, the inner cutting element 400 may include a protrusion (not shown) formed on a side surface thereof instead of the groove 406. Further, in one or more embodiments, the sleeve 410 may include a corresponding groove (not shown) configured to engage or interface with the protrusion of the inner cutting element 400 instead of the protrusion 408. As such, in one or more embodiments, axial movement or displacement of the inner cutting element 400 with respect to the sleeve 410 may be limited by an engagement between the protrusion of the inner cutting element and the groove of the sleeve 410.

Accordingly, in one or more embodiments, the inner cutting element 400 may include a smooth and curved transition between a protrusion formed on a side surface thereof and the neighboring side surface and/or curved side surfaces. Further, in one or more embodiments, the sleeve 410 may include corresponding smooth and curved transitions between the groove of the sleeve 410 and the neighboring side surfaces and/or curved side surface to engage or interface with the inner cutting element 400. In one or more embodiments, the side surface of the inner cutting element is a continuously curved surface. Optionally, the inner cutting element 400 may also include smooth and curved transitions 411 between the side surface, e.g., an outer surface of the substrate 404, and the bottom surface 409 of the inner cutting element.

Those having ordinary skill in the art will appreciate that the smooth and curved transitions discussed above with regard to the inner cutting element 400 and the sleeve 410 may of any radius known in the art. In other words, embodiments disclosed herein may include smooth and curved transitions having any radius of curvature known in the art. Further, those having ordinary skill in the art will appreciate that the smooth and curved transitions discussed above are not limited to circular curves and arcs. For example, the smooth and curved transitions discussed above may be elliptical, or otherwise irregular, in profile, such that the smooth or curved transitions do not include sharp edges or corners. As used herein, “smooth and curved transitions” refer to transitions between surfaces that do not include sharp edges or corners.

As the inner cutting element 400 may be rotatable within the sleeve 410, the smooth and curved transitions 407 between the groove 406 and the neighboring side surfaces may reduce friction between the inner cutting element 400 and the sleeve 410. Reduced friction between the inner cutting element 400 and the sleeve 410 may extend the life of the inner cutting element 400, as the inner cutting element 400 is exposed to external forces and conditions that may force the inner cutting element 400 against the sleeve 410, axially, and may also force the inner cutting element 400 to rotate within the sleeve 410.

Referring to FIG. 5, an inner cutting element 500 disposed within a sleeve 510 (optionally a multi-piece sleeve, as described above), in which a bottom surface. 509 of the inner cutting element 500 has curvature, in accordance with embodiments disclosed herein, is shown.

In one or more embodiments, the inner cutting element 500 may be a rotatable cutting element that may be rotatable within the sleeve 510. Further, in one or more embodiments, the inner cutting element 500 may include an ultrahard layer 502 and a substrate 504. In one or more embodiments, the inner cutting element 500 may have a groove 506 formed in a side surface thereof. As shown, the inner cutting element 500 has the groove 506 formed in the substrate 504.

In one or more embodiments, at least one component may interface at least a portion of the groove 506 to limit axial movement of the inner cutting element 500 with respect to the sleeve 510. As shown, the sleeve 510 includes a protrusion 508 that is configured to engage or interface with the groove 506 of the inner cutting element 500. In one or more embodiments, the axial movement or displacement of the inner cutting element 500 may be limited by this engagement between the at least one component (e.g., the protrusion 508 of the sleeve 510) and the groove 506 of the inner cutting element 500.

As shown, the inner cutting element 500 includes smooth and curved transitions 511 between the side surface, e.g., an outer surface of the substrate 504, and the bottom surface 509 of the inner cutting element. Accordingly, in one or more embodiments, the sleeve 510 includes corresponding smooth and curved transitions between an inner side surface of the sleeve 510 and the neighboring inner bottom surface of the sleeve 510 to engage or interface with the curved bottom surface 509 of the inner cutting element 500.

Further, as shown, the bottom surface 509 of the inner cutting element 500 has curvature. In other words, in one or more embodiments, the bottom surface 509 of the cutting element 500 is a curved surface. As shown, the bottom surface 509 of the cutting element 500 is a curved surface and is convex in shape. In one or more embodiments, the inner surface of the sleeve 510 that may engage the bottom surface 509 of the inner cutting element 500 may not be conformed to the curved bottom surface 509 of the inner cutting element 500. In other words, although the bottom surface 509 of the inner cutting element 500 may be curved and convex, the contacting surface of the sleeve 510 may not necessarily be curved or concave. Rather, in one or more embodiments, the contacting surface of the sleeve 510 may be straight such that contact between the bottom surface 509 of the inner cutting element 500 and the sleeve 510 is minimized.

Alternatively, in one or more embodiments, the contacting surface of the sleeve 510 may be a curved surface, but may curve away, or in an opposite direction, to the curved bottom surface 509 of the inner cutting element 500 such that contact and surface area between the inner cutting element 500 and the sleeve 510 is minimized. Other examples of cutting elements with curved or conic-shaped surfaces are included in U.S. Provisional Application No. 61/479,183, which is herein incorporated by reference in its entirety.

As the inner cutting element 500 may be rotatable within the sleeve 510, the curved bottom surface 509 of the inner cutting element 500 may minimize the surface area of the bottom surface 509 that contacts the sleeve 510. The surface area of contact between the bottom surface 509 of the inner cutting element 500 and the sleeve 510 may be minimized by creating a point of contact between the bottom surface 509 of the inner cutting element 500 and the sleeve 510, as opposed to the entire bottom surface 509 contacting the sleeve 510. Minimization of the surface area of the bottom surface 509 of the inner cutting element 500 that may contact the inner surface of the sleeve 510 may result in reduced friction between the inner cutting element 500 and the sleeve 510. As discussed above, reduced friction between the inner cutting element 500 and the sleeve 510 may extend the life of the inner cutting element 500, as the inner cutting element 500 is exposed to external forces and conditions that may force the inner cutting element 500 against the sleeve 510, axially, and may also force the inner cutting element 500 to rotate within the sleeve 510.

In one or more embodiments, one or more ball bearings or roller bearings (not shown) may be disposed along the outer diameter of the inner cutting element 500 and/or op the bottom surface 509 of the inner cutting element 500 to minimize friction between the inner cutting element 500 and the sleeve 510.

Referring to FIGS. 6A and 6B, an inner cutting element 600 having a protrusion 606 formed on a side surface thereof, in which the groove 606 extends around only a portion of the inner cutting element 600, is shown.

In one or more embodiments, the inner cutting element 600 may include an ultrahard layer 602 and a substrate 604. In one or more embodiments, the inner cutting element 600 may have the groove 606 formed in a side surface thereof. As shown, the inner cutting element 600 has the groove 606 formed in the substrate 604, where groove only extends around a portion of the circumference of the inner cutting element 600. Cutting element 600 may be retained in a sleeve 610 (optionally a multi-piece sleeve, as described above).

In one or more embodiments, at least one interfacing component may interface at least a portion of the groove 606 to limit axial movement of the inner cutting element 600 with respect to the sleeve 610. In one or more embodiments, the sleeve 610 may include a protrusion (not shown) that is configured to engage or interface with the groove 606 of the inner cutting element 600. In one or more embodiments, the axial movement or displacement of the inner cutting element 600 may be limited by this engagement between the at least one interfacing component (e.g., the protrusion of the sleeve 610) and the groove 606 of the inner cutting element 600.

In one or more embodiments, the corresponding protrusion (or groove) of the sleeve 610 may not extend around the entire circumference of the inner cutting element and may be formed to engage with the groove 606 (or protrusion) of the inner cutting element 600. In other words, in one or more embodiments, the dimensions of the protrusion of the sleeve 610 may substantially match the dimensions of the groove 606 of the inner cutting element 600, such that the protrusion of the sleeve 610 may be formed to interface or engage with the corresponding groove 606 formed in the inner cutting element 600. This may restrict both rotation of the inner cutting element 600 within the sleeve 610 and axial movement or displacement of the inner cutting element 600 with respect to the sleeve 610.

Referring to FIG. 7, an inner cutting element 700 disposed within a sleeve 710 (optionally, a multi-piece sleeve, as discussed above), in which an outer diameter DS of the sleeve 710 is equal to an outer diameter DC of the inner cutting element 700, is shown.

In one or more embodiments, the inner cutting element 700 may include an ultrahard layer 702 and a substrate 704. In one or more embodiments, the inner cutting element 700 may have the groove 706 formed in a side surface thereof. As shown, the inner cutting element 700 has the groove 706 formed in the substrate 704.

In one or more embodiments, at least one interfacing component may interface at least a portion of the groove 706 to limit axial movement of the inner cutting element 700 with respect to the sleeve 710. In one or more embodiments, the sleeve 710 may include a protrusion 708 that is configured to engage or interface with the groove 706 of the inner cutting element 700. In one or more embodiments, the axial movement or displacement of the inner cutting element 700 may be limited by this engagement between the at least one component (e.g., the protrusion 708 of the sleeve 710) and the groove 706 of the inner cutting element 700.

As shown, the inner cutting element 700 is disposed within the sleeve 710. In one or more embodiments, the inner cutting element 700 may be a rotatable cutting element that may be rotatable within the sleeve 710. As shown, the outer diameter DS of the sleeve 710 is substantially equal to the outer diameter DC of the inner cutting element 700.

As shown in FIG. 8, an inner cutting element 800 disposed within a sleeve 810 (optionally a multi-piece sleeve, as described above), in which the inner cutting element 800 includes a smooth and curved transition 807 between a groove 806 and a neighboring side surface, and in which an outer diameter DS of the sleeve 810 is equal to an outer diameter DC of the inner cutting element 800, in accordance with embodiments disclosed herein, is shown.

In one or more embodiments, the inner cutting element 800 may be a rotatable cutting element that may be rotatable within the sleeve 810. Further, in one or more embodiments, the inner cutting element 800 may include an ultrahard layer 802 and a substrate 804. In one or more embodiments, the inner cutting element 800 may have the groove 806 formed in a side surface thereof. As shown, the inner cutting element 800 has the groove 806 formed in the substrate 804.

In one or more embodiments, at least one component may interface at least a portion of the groove 806 to limit axial movement of the inner cutting element 800 with respect to the sleeve 810. As shown, the sleeve 810 includes a protrusion 808 that is configured to engage or interface with the groove 806 of the inner cutting element 800. In one or more embodiments, the axial movement or displacement of the inner cutting element 800 may be limited by this engagement between the at least one interfacing component (e.g., the protrusion 808 of the sleeve 810) and the groove 806 of the inner cutting element 800. As shown, the outer diameter DS of the sleeve 810 is substantially equal to the outer diameter DC of the inner cutting element 800.

Further, as shown, the inner cutting element 800 includes smooth and curved transitions 807 between the groove 806 and the neighboring side surface, e.g., an outer surface of the substrate 804. Accordingly, in one or more embodiments, the sleeve 810 includes corresponding smooth and curved transitions between the protrusion 808 and the neighboring side surfaces, e.g., an inner surface of the sleeve 810, to engage or interface with the inner cutting element 800.

As discussed above, in one or more embodiments, the inner cutting element 800 may include a protrusion (not shown) formed on a side surface thereof instead of the groove 806. Further, in one or more embodiments, the sleeve 810 may include a corresponding groove (not shown) configured to engage or interface with the protrusion of the inner cutting element 800 instead of the protrusion 808. As such, in one or more embodiments, axial movement or displacement of the inner cutting element 800 with respect to the sleeve 810 may be limited by an engagement between the protrusion of the inner cutting element and the groove of the sleeve 810.

Accordingly, in one or more embodiments, the inner cutting element 800 may include a smooth and curved transition between a protrusion formed on a side surface thereof and the neighboring side surface and/or curved side surfaces. Further, in one or more embodiments, the sleeve 810 may include corresponding smooth and curved transitions between the groove of the sleeve 810 and the neighboring side surfaces and/or curved side surface to engage or interface with the inner cutting element 800. In one or more embodiments, the side surface of the inner cutting element is a continuously curved surface. Optionally, the inner cutting element 800 may also include smooth and curved transitions 811 between the side surface, e.g., an outer surface of the substrate 804, and the bottom surface 809 of the inner cutting element.

Those having ordinary skill in the art will appreciate that the smooth and curved transitions discussed above with regard to the inner cutting element 800 and the sleeve 810 may of any radius known in the art. In other words, embodiments disclosed herein may include smooth and curved transitions having any radius of curvature known in the art. Further, those having ordinary skill in the art will appreciate that the smooth and curved transitions discussed above are not limited to circular curves and arcs. For example, the smooth and curved transitions discussed above may be elliptical, or otherwise irregular, in profile, such that the smooth or curved transitions do not include sharp edges or corners. As used herein, “smooth and curved transitions” refer to transitions between surfaces that do not include sharp edges or corners.

As the inner cutting element 800 may be rotatable within the sleeve 810, the smooth and curved transitions 807 between the groove 806 and the neighboring side surfaces may reduce friction between the inner cutting element 800 and the sleeve 810. Reduced friction between the inner cutting element 800 and the sleeve 810 may extend the life of the inner cutting element 800, as the inner cutting element 800 is exposed to external forces and conditions that may force the inner cutting element 800 against the sleeve 810, axially, and may also force the inner cutting element 800 to rotate within the sleeve 810.

In one or more embodiments, a cutting tool may include a tool body, a plurality of blades extending from the tool body, at least one cutter pocket formed in the plurality of blades, at least one cutter assembly disposed in the at least one cutter pocket, the at least one cutter assembly including a multi-piece split sleeve, an inner cutting element having a groove or protrusion formed in a side surface thereof and disposed in the multi-piece split sleeve, and at least one component interfacing at least a portion of the groove or the protrusion to limit axial movement of the inner cutting element with respect to the multi-piece split sleeve, in which the multiple pieces of the split sleeve are joined together at an overlapping joint, in which the multi-piece sleeve is brazed into the at least one cutter pocket.

Referring back to FIG. 2, the inner cutting element 200 may be a rotatable cutting element that may be rotatable within the multi-piece split sleeve 210. The inner cutting element 200 may be disposed within the multi-piece split sleeve 210, which may be disposed in a cutter pocket formed on at least one blade on a tool body. As discussed above, the sleeve 210 may include at least one overlapping joint 212 formed at any point where any pieces of the split sleeve 210 are joined together or engaged. The multi-piece sleeve may be brazed into the at least one cutter pocket. As discussed above, an overlapping joint (e.g., the overlapping joint 212) may be sufficient to resist capillary flow of braze material between the pieces of the split sleeve 210.

In one or more embodiments, a cutting tool may include a tool body, a plurality of blades extending from the tool body, at least one rotatable cutting element disposed on at least one blade, in which the rotatable cutting element has a groove formed in a side surface thereof, and at least one retention element interfacing the rotatable cutting element at the groove and limiting axial movement of the rotatable cutting element, in which the rotatable cutting element includes a smooth and curved transition between the groove and the neighboring side surface. In one or more embodiments, the rotating cutting element may include a smooth and curved transition between the side surface and a bottom surface of the rotatable cutting element and/or curved side surfaces and/or bottom surface

Further, in one or more embodiments, the rotatable cutting element may be disposed in a sleeve, in which the sleeve may be brazed into a cutter pocket formed in the at least one blade. In one or more embodiments, the rotatable cutting element may be disposed in a cutter pocket without a sleeve. In one or more embodiments, the sleeve may be a multi-piece sleeve (i.e., the multi-piece sleeve 210 of FIG. 2), in which the multiple pieces of the split sleeve are joined together at an overlapping joint (i.e., the overlapping joint 212 of FIG. 2).

According to some embodiments, a multi-piece sleeve or a combination of the sleeve and cutter pocket may extend greater than 180 degrees around the circumference of the inner cutting element to radially retain in the inner cutting element within the cutter pocket. For example, a cutter assembly may include a multi-piece sleeve and an inner cutting element having a groove or protrusion formed in a circumferential side surface thereof and disposed in the sleeve. At least one component may interface at least a portion of the groove or the protrusion to limit axial movement of the inner cutting element with respect to the multi-piece sleeve, while the multi-piece sleeve or a combination of the sleeve and cutter pocket may extend greater than 180 degrees around the circumference of the inner cutting element to radially retain in the inner cutting element within the cutter pocket.

For example, FIGS. 9-11 show a cutter assembly that has an inner cutting element retained within a cutter pocket using a combination of a sleeve and the cutter pocket inner side surface to extend around greater than 180 degrees of the outer circumferential side surface of the inner cutting element. As shown in FIGS. 9-11, a segment of a bit blade 2000 has an inner cutting element 2020 assembled within a cutter pocket 2010. Particularly, the inner cutting element 2020 has a cutting face 2022, an outer circumferential surface 2024, and a circumferential channel or groove 2026 formed within the outer circumferential surface 2024. The cutter pocket 2010 has a back surface 2012 and an inner side surface 2014, wherein a receptacle 2015 (represented by the shaded area) is formed within the side surface 2014 to receive a partial sleeve 2040. The receptacle 2015 extends from the leading side 2002 of the blade 2000 a distance D along the length of the cutter pocket 2010 and a radial distance around the side surface of the cutter pocket 2010. A partial sleeve 2040 may be positioned adjacent to the inner cutting element 2020, such that the partial sleeve 2040 extends partially around the outer circumferential surface 2024 of the inner cutting element 2020. In the embodiment shown in FIGS. 9-11, the sleeve 2040 is a partial sleeve formed of a single piece. However, in other embodiments, the sleeve may be a multi-piece split sleeve, as discussed above. Further, the partial sleeve 2040 may have a lip or a protrusion 2046 formed thereon that mates with the circumferential groove 2026 of the inner cutting element 2020. The inner cutting element 2020 and the partial sleeve 2040 may then be inserted into the cutter pocket 2010. The partial sleeve 2040 may be attached to the cutter pocket 2010 to form part of the cutter pocket side surface, wherein the inner cutting element 2020 may rotate within the cutter pocket 2010 and partial sleeve 2040. Methods of attaching the partial sleeve 2040 to the rolling cutter pocket 2010 may include, for example, brazing, welding, or mechanical locking.

As shown, the partial sleeve 2040 and the cutter pocket side surface 2014 may form an arc A. The arc may extend around the inner cutting element 2020 greater than 180 degrees. Thus, in such embodiments, the cutter pocket and the partial sleeve may function similar to the multi-piece split sleeves described above, wherein the cutter pocket forms one or more pieces surrounding the inner cutting element and the partial sleeve forms another piece surrounding the inner cutting element. Advantageously, in some embodiments having an arc extending greater than 180 degrees, an inner cutting element may be retained within a cutter pocket using only the side surface of the cutter pocket and the partial sleeve. For example, a side surface retention mechanism (the mating protrusion (or groove) formed along the cutter pocket side surface/partial sleeve and circumferential groove (or protrusion) formed within the inner cutting element) may retain the inner cutting element axially within the cutter pocket and sleeve, while the extension of the cutter pocket side surface (in combination with the partial sleeve) greater than 180 degrees may inhibit the inner cutting element from being dislodged (pulled out from the top face) from the cutter pocket.

Further, the shape of a partial sleeve and a corresponding receptacle may vary. For example, as shown in FIGS. 12 and 13, two partial sleeves according to embodiments of the present disclosure are shown. A partial sleeve 2340 has a lower surface 2341 and an upper surface 2342, wherein the upper surface 2342 is positioned adjacent to a rolling cutter and forms at least part of the side surface of a rolling cutter pocket once inserted into a rolling cutter pocket receptacle. Particularly, the upper surface 2342 of a partial sleeve 2340 may have an arc shape, which extends around part of the circumference of a rolling cutter once the partial sleeve 2340 is assembled with a rolling cutter. Further, as described above, the upper surface 2342 of a partial sleeve 2340 may have at least one lip 2346 (and/or at least one channel) formed thereon. The shape of a partial sleeve may be described with reference to its width W (the distance the partial sleeve extends from a leading face of a blade into the rolling cutter pocket), depth D (the distance between the upper surface of the partial sleeve to the lower surface of the partial sleeve), and arc length L (the distance around the arc of the upper surface). As shown in FIG. 12, the depth D of the partial sleeve 2340 may extend a constant distance from the upper surface 2342 to the lower surface 2341 of the partial sleeve 2340, as measured around the arc length L. Thus, in such embodiments, the cross-sectional shape along the length of the partial sleeve 1740 may be an arc, or partial-circular shape. Alternatively, as shown in FIG. 13, the depth D of the partial sleeve 2340 may extend a varying distance from the upper surface 2342 to the lower surface 2341 of the partial sleeve 2340, as measured around the arc length L. In such embodiments, the cross-sectional shape along the length of the partial sleeve may be irregular shapes. Additionally, the width W of a partial sleeve 2340 may constant or varying, as measured around the arc length L. One skilled in the art may appreciate that receptacles according to embodiments of the present disclosure may have corresponding shapes to the partial sleeve shapes described above. Particularly, a receptacle may have a negative shape (i.e., the shape of the void, or empty space) that mates with a corresponding partial sleeve.

In embodiments using a sleeve, such sleeve may be fixed to the bit body (or other cutting tool) by any means known in the art, including by casting in place during sintering the bit body (or other cutting tool) or by brazing the element in place in the cutter pocket (not shown). Brazing may occur before or after the inner rotatable cutting element is retained within the sleeve; however, in particular embodiments, the inner rotatable cutting element is retained in the sleeve before the sleeve is brazed into place. Further, in embodiments using a multi-piece sleeve, one or more pieces of the sleeve may be cast in place during sintering the bit body and one or more pieces of the sleeve may be fixed to the bit body by other means, such as brazing. For example, referring again to FIGS. 9-11, the inner side surface 2014 of the cutter pocket 2010 may be formed from pieces of a multi-piece sleeve that are cast in place during sintering of the bit body, while the partial sleeve 2040 may be another piece of the multi-piece sleeve that is brazed in place.

Each of the embodiments described herein have at least one ultrahard material included therein. Such ultra hard materials may include a conventional polycrystalline diamond table (a table of interconnected diamond particles having interstitial spaces therebetween in which a metal component (such as a metal catalyst) may reside, a thermally stable diamond layer (i.e., having a thermal stability greater than that of conventional polycrystalline diamond, 750° C.) formed, for example, by removing substantially all metal from the interstitial spaces between interconnected diamond particles or from a diamond/silicon carbide composite, or other ultra hard material such as a cubic boron nitride. Further, in particular embodiments, the inner rotatable cutting element may be formed entirely of ultrahard material(s), but the element may include a plurality of diamond grades used, for example, to form a gradient structure (with a smooth or non-smooth transition between the grades). In a particular embodiment, a first diamond grade having smaller particle sizes and/or a higher diamond density may be used to form the upper portion of the inner rotatable cutting element (that forms the cutting edge when installed on a bit or other tool), while a second diamond grade having larger particle sizes and/or a higher metal content may be used to form the lower, non-cutting portion of the cutting element. Further, it is also within the scope of the present disclosure that more than two diamond grades may be used.

As known in the art, thermally stable diamond may be formed in various manners. A typical polycrystalline diamond layer includes individual diamond “crystals” that are interconnected. The individual diamond crystals thus form a lattice structure. A metal catalyst, such as cobalt, may be used to promote recrystallization of the diamond particles and formation of the lattice structure. Thus, cobalt particles are typically found within the interstitial spaces in the diamond lattice structure. Cobalt has a significantly different coefficient of thermal expansion as compared to diamond. Therefore, upon heating of a diamond table, the cobalt and the diamond lattice will expand at different rates, causing cracks to form in the lattice structure and resulting in deterioration of the diamond table.

To obviate this problem, strong acids may be used to “leach” the cobalt from a polycrystalline diamond lattice structure (either a thin volume or entire tablet) to at least reduce the damage experienced from heating diamond-cobalt composite at different rates upon heating. Examples of “leaching” processes can be found, for example, in U.S. Pat. Nos. 4,288,248 and 4,104,344. Briefly, a strong acid, typically hydrofluoric acid or combinations of several strong acids may be used to treat the diamond table, removing at least a portion of the co-catalyst from the PDC composite. Suitable acids include nitric acid, hydrofluoric acid, hydrochloric acid, sulfuric acid, phosphoric acid, or perchloric acid, or combinations of these acids. In addition, caustics, such as sodium hydroxide and potassium hydroxide, have been used to the carbide industry to digest metallic elements from carbide composites. In addition, other acidic and basic leaching agents may be used as desired. Those having ordinary skill in the art will appreciate that the molarity of the leaching agent may be adjusted depending on the time desired to leach, concerns about hazards, etc.

By leaching out the cobalt, thermally stable polycrystalline (TSP) diamond may be formed. In certain embodiments, only a select portion of a diamond composite is leached, in order to gain thermal stability without losing impact resistance. As used herein, the term TSP includes both of the above (i.e., partially and completely leached) compounds. Interstitial volumes remaining after leaching may be reduced by either furthering consolidation or by filling the volume with a secondary material, such by processes known in the art and described in U.S. Pat. No. 5,127,923, which is herein incorporated by reference in its entirety.

Alternatively, TSP may be formed by forming the diamond layer in a press using a binder other than cobalt, one such as silicon, which has a coefficient of thermal expansion more similar to that of diamond than cobalt has. During the manufacturing process, a large portion, 80 to 100 volume percent, of the silicon reacts with the diamond lattice to form silicon carbide which also has a thermal expansion similar to diamond. Upon heating, any remaining silicon, silicon carbide, and the diamond lattice will expand at more similar rates as compared to rates of expansion for cobalt and diamond, resulting in a more thermally stable layer. PDC cutters having a TSP cutting layer have relatively low wear rates, even as cutter temperatures reach 1200° C. However, one of ordinary skill in the art would recognize that a thermally stable diamond layer may be formed by other methods known in the art, including, for example, by altering processing conditions in the formation of the diamond layer.

The substrate on which the cutting face is optionally disposed may be formed of a variety of hard or ultra hard particles. In one embodiment, the substrate may be formed from a suitable material such as tungsten carbide, tantalum carbide, or titanium carbide. Additionally, various binding metals may be included in the substrate, such as cobalt, nickel, iron, metal alloys, or mixtures thereof. In the substrate, the metal carbide grains are supported within the metallic binder, such as cobalt. Additionally, the substrate may be formed of a sintered tungsten carbide composite structure. It is well known that various metal carbide compositions and binders may be used, in addition to tungsten carbide and cobalt. Thus, references to the use of tungsten carbide and cobalt are for illustrative purposes only, and no limitation on the type substrate or binder used is intended. In another embodiment, the substrate may also be formed from a diamond ultra hard material such as polycrystalline diamond and thermally stable diamond. While the illustrated embodiments show the cutting face and substrate as two distinct pieces, one of skill in the art should appreciate that it is within the scope of the present disclosure the cutting face and substrate are integral, identical compositions. In such an embodiment, it may be preferable to have a single diamond composite forming the cutting face and substrate or distinct layers. Specifically, in embodiments where the cutting element is a rotatable cutting element, the entire cutting element may be formed from an ultrahard material, including thermally stable diamond (formed, for example, by removing metal from the interstitial regions or by forming a diamond/silicon carbide composite).

The sleeve may be formed from a variety of materials. In one embodiment, the sleeve may be formed of a suitable material such as tungsten carbide, tantalum carbide, or titanium carbide. Additionally, various binding metals may be included in the outer support element, such as cobalt, nickel, iron, metal alloys, or mixtures thereof, such that the metal carbide grains are supported within the metallic binder. In a particular embodiment, the outer support element is a cemented tungsten carbide with a cobalt content ranging from 6 to 13 percent. It is also within the scope of the present disclosure that the sleeve and/or substrate may also include one more lubricious materials, such as diamond to reduce the coefficient of friction therebetween. The components may be formed of such materials in their entirely or have portions of the components including such lubricious materials deposited on the component, such as by chemical plating, chemical vapor deposition (CVD) including hollow cathode plasma enhanced CVD, physical vapor deposition, vacuum deposition, arc processes, or high velocity sprays). In a particular embodiment, a diamond-like coating may be deposited through CVD or hallow cathode plasma enhanced CVD, such as the type of coatings disclosed in US 2010/0108403, which is assigned to the present assignee and herein incorporated by reference in its entirety.

In other embodiments, the sleeve may be formed of alloy steels, nickel-based alloys, and cobalt-based alloys. One of ordinary skill in the art would also recognize that cutting element components may be coated with a hardfacing material for increased erosion protection. Such coatings may be applied by various techniques known in the art such as, for example, detonation gun (d-gun) and spray-and-fuse techniques.

The cutting elements of the present disclosure may be incorporated in various types of cutting tools, including for example, as cutters in fixed cutter bits or hole enlargement tools such as reamers. Bits having the cutting elements of the present disclosure may include a single rotatable cutting element with the remaining cutting elements being conventional cutting elements, all cutting elements being rotatable, or any combination therebetween of rotatable and conventional cutting elements.

In some embodiments, the placement of the cutting elements on the blade of a fixed cutter bit may be selected such that the rotatable cutting elements are placed in areas experiencing the greatest wear. For example, in a particular embodiment, rotatable cutting elements may be placed on the shoulder or nose area of a fixed cutter bit. Additionally, one of ordinary skill in the art would recognize that there exists no limitation on the sizes of the cutting elements of the present disclosure. For example, in various embodiments, the cutting elements may be formed in sizes including, but not limited to, 9 mm, 13 mm, 16 mm, and 19 mm.

Further, one of ordinary skill in the art would also appreciate that any of the design modifications as described above, including, for example, side rake, back rake, variations in geometry, surface alteration/etching, seals, bearings, material compositions, etc, may be included in various combinations not limited to those described above in the cutting elements of the present disclosure. In one embodiment, a cutter may have a side rake ranging from 0 to ±45 degrees. In another embodiment, a cutter may have a back rake ranging from about 5 to 35 degrees.

A cutter may be positioned on a blade with a selected back rake to assist in removing drill cuttings and increasing rate of penetration. A cutter disposed on a drill bit with side rake may be forced forward in a radial and tangential direction when the bit rotates. In some embodiments because the radial direction may assist the movement of inner rotatable cutting element relative to outer support element, such rotation my allow greater drill cuttings removal and provide an improved rate of penetration. One of ordinary skill in the art will realize that any back rake and side rake combination may be used with the cutting elements of the present disclosure to enhance rotatability and/or improve drilling efficiency.

As a cutting element contacts formation, the rotating motion of the cutting element may be continuous or discontinuous. For example, when the cutting element is mounted with a determined side rake and/or back rake, the cutting force may be generally pointed in one direction. Providing a directional cutting force may allow the cutting element to have a continuous rotating motion, further enhancing drilling efficiency.

Embodiments of the present disclosure may provide at least one of the following advantages. The use of an inner cutting element with a curved or convex bottom surface may minimize the contact area between the bottom surface of the inner cutting element and the sleeve. Because the contact area between the bottom surface of the inner cutting element and the sleeve may be minimized, friction may be reduced between the bottom surface of the inner cutting element and the sleeve may be minimized, which may extend the life of the inner cutting element. Further, the use of a multi-piece split sleeve may allow side retention of an inner cutting element within a cutting assembly without obstructing any portion of the cutting surface on top of the inner cutting element. Further, the use of a multi-piece split sleeve having one or more overlap joints located where any pieces of the split sleeve are joined together or engaged may allow for the side retention of the inner cutting element discussed above, while also sufficiently to resisting capillary flow of braze material between the pieces of the split sleeve.

Although only a few example embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the example embodiments without materially departing from this invention. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. §112, paragraph 6 for any limitations of any of the claims herein, except for those in which the claim expressly uses the words ‘means for’ together with an associated function. 

1. A cutter assembly, comprising: a multi-piece split sleeve; an inner cutting element having a groove or protrusion formed in a side surface thereof and disposed in the multi-piece split sleeve; and at least one component interfacing at least a portion of the groove or the protrusion to limit axial movement of the inner cutting element with respect to the multi-piece split sleeve, wherein the multiple pieces of the split sleeve are joined together at an overlapping joint.
 2. The cutter assembly of claim 1, wherein the inner cutting element is rotatable within the multi-piece split sleeve.
 3. The cutter assembly of claim 1, wherein the sleeve split comprises at least two inner surface radii, a first sleeve radius being smaller than a second sleeve radius, wherein the inner cutting element comprises a side surface having at least two radii, a first cutting element radius being smaller than a second cutting element radius and axially positioned between a cutting face and the second cutting element radius, and wherein the sleeve is adjacent to at least a portion of the inner cutting element side surface, such that the first sleeve radius mates with the first cutting element radius and the second sleeve radius mates with the second cutting element radius.
 4. The cutter assembly of claim 1, wherein a groove or protrusion extend circumferentially around at least a portion of the inner cutting element.
 5. (canceled)
 6. The cutter assembly of claim 1, wherein the interfacing component is the sleeve.
 7. The cutter assembly of claim 1, wherein the interfacing component is a separate component from the sleeve.
 8. The cutter assembly of claim 1, wherein the multi-piece split sleeve extends around only a portion of the circumference of the inner cutting element.
 9. The cutter assembly of claim 1, wherein the multi-piece split sleeve extends around greater than 180 degrees of the inner cutting element and up to the entire circumference of the inner cutting element.
 10. (canceled)
 11. The cutter assembly of claim 1, wherein the inner cutting element comprises a smooth and curved transition between neighboring surfaces defining different inner cutting element radii.
 12. (canceled)
 13. The cutter assembly of claim 1, wherein the inner cutting element consists of diamond.
 14. The cutter assembly of claim 1, wherein a bottom surface of the inner cutting element has curvature.
 15. A cutting tool, comprising: a tool body; a plurality of blades extending from the tool body; at least one cutter pocket formed in the plurality of blades; at least one cutter assembly of claim 1 disposed in the at least one cutter pocket.
 16. (canceled)
 17. (canceled)
 18. (canceled)
 19. (canceled)
 20. (canceled)
 21. (canceled)
 22. (canceled)
 23. (canceled)
 24. (canceled)
 25. (canceled)
 26. (canceled)
 27. The cutting tool of claim 15, wherein the overlapping joint is sufficient to resist capillary flow of braze therethrough.
 28. (canceled)
 29. (canceled)
 30. The cutting tool of claim 15, wherein at least one piece of the multi-piece sleeve is cast into the blade.
 31. The cutting tool of claim 15, wherein at least one piece of the multi-piece sleeve is brazed into the cutter pocket.
 32. A cutting tool, comprising: a tool body; a plurality of blades extending from the tool body; at least one rotatable cutting element disposed on at least one blade, wherein the rotatable cutting element has a groove formed in a side surface thereof; and at least one retention element interfacing the rotatable cutting element at the groove and limiting axial movement of the rotatable cutting element, wherein the rotatable cutting element comprises a smooth and curved transition between the groove and the neighboring side surface.
 33. The cutting tool of claim 32, wherein the rotatable cutting element comprises a smooth and curved transition between the side surface and a bottom surface of the rotatable cutting element.
 34. The cutting tool of claim 32, wherein the rotatable cutting element is disposed in a sleeve, where the sleeve is brazed in a cutter pocket formed in the at least one blade.
 35. The cutting tool of claim 34, wherein the sleeve is a multi-piece sleeve.
 36. The cutting tool of claim 35, wherein the multiple pieces of the split sleeve are joined together at an overlapping joint.
 37. The cutting tool of claim 35, wherein the multi-piece sleeve comprises a sleeve component and the cutter pocket.
 38. The cutting tool of claim 32, wherein the rotatable cutting element is disposed in a cutter pocket.
 39. A cutting tool, comprising: a tool body; a plurality of blades extending from the tool body; at least one rotatable cutting element disposed in a cutter pocket on at least one blade, wherein the rotatable cutting element has a groove formed in a side surface thereof; and at least one retention element interfacing the rotatable cutting element; wherein the at least one retention element extends greater than 180 degrees and less than 360 degrees around the rotatable cutting element.
 40. The cutting tool of claim 39, wherein the at least one retention element comprises a protrusion that mates with the groove and limits axial movement of the rotatable cutting element.
 41. The cutting tool of claim 39, wherein the at least one retention element comprises a multi-piece sleeve.
 42. The cutting tool of claim 41, wherein at least one piece of the multi-piece sleeve is cast into the blade.
 43. The cutting tool of claim 39, wherein at least one piece of the multi-piece sleeve is brazed into the blade.
 44. The cutting tool of claim 38, wherein the at least one retention mechanism comprises a sleeve and a portion of the cutter pocket. 